Effect of Mechanical Properties of Al2O3/(W,Ti)C Ceramic Tool Material on Its Tribological Characterization

Ceramic cutting tools are mainly used in high-speed dry machining, thus the tool material is in high temperature friction state with the workpiece material during cutting. The tribological characterizations have a direct impact on the cutting performance of the tool. Therefore, tribological characterizations of two kinds of ceramic tool materials with different mechanical properties against hardened steel H13 were compared at the same temperature, one material is Al2O3/(W,Ti)C/Ni with Ni(marked as AWTN), another is Al2O3/(W,Ti)C without Ni(marked as AWT). Also, the variation of tribological characterizations of AWT ceramic tool material with different temperatures was emphatically investigated. The results showed that the average friction coefficients of AWT and AWTN decreased with the increase of sliding speed under the same load, and the friction coefficient of AWT was lower than that of AWTN. Although AWTN material had better flexural strength and fracture toughness than AWT at ambient temperature, yet better hardness of AWT material both at room temperature and high temperature led to the lower friction coefficient and lower wear rate, indicating that the hardness had a greater impact on the wear of ceramic tool materials. The friction coefficient of AWT decreased with the increase of load and increased with the increase of temperature. The wear mechanism of Al2O3/(W,Ti)C ceramic tool material was different at different temperatures. The conclusion of this research had important guiding significance for the selection of cutting tools and cutting parameters in order to improve the machining quality.

Mechanical Properties and Microstructures of Al2O3/TiC/TiB2 Ceramic Tool Material

In order to develop a new ceramic tool material with self-repairing capability, Al2O3/TiC/TiB2 ceramic tool material was prepared by vacuum hot-pressure sintering method. The toughening and strengthening mechanism of TiB2 on Al2O3/TiC substrate was analyzed. The results show that the ceramic tool material has good comprehensive mechanical properties when the TiB2 content is 10 vol.%. Its flexural strength was 701.32 MPa, hardness was 18.3 GPa, and fracture toughness was 6.2 MPa·m1/2, which were improved by 11.6%, 2.2% and 16.1% respectively, compared with the Al2O3/TiC tool material. Fracture surfaces of the Al2O3/TiC/TiB2 ceramic tool material were characterized by SEM, EDS and XRD. The results showed that the fracture mode was a mixture of transgranular fracture and intergranular fracture. The growth of Al2O3 and TiC grains can be effectively inhibited by adding appropriate amount of TiB2, and the internal grains of the material can be refined. The TiB2 has a uniform distribution in the matrix and acts as a diffusion toughening agent. The cutting performance of Al2O3/TiC/10 vol.%TiB2 tool material was further investigated. Experiments conducted on tools made of Al2O3/TiC and Al2O3/TiC/TiB2 materials showed that the main forms of wear for both tools were abrasive wear and bonded wear. The friction coefficient of Al2O3/TiC/TiB2 tools was reduced by 10.77% compared to Al2O3/TiC tools.